Patent GB-909181-A (GB)
Title: Method of and apparatus for controlling the velocity of wheeled vehicles
Inventor: BICK DAVID EDWART
IPC: B61K7/00
Filed: 1959-05-11
Abstract: 909,181. Track brakes. DOWTY HYDRAULIC UNITS Ltd. May 3, 1960 [May 11, 1959; Aug. 28, 1959; Sept. 14, 1959; Nov. 2, 1959], Nos. 16082/59, 29473/59, 31278/59 and 37139/59. Class 103 (1). [Also in Group XXX] A rail vehicle speed-control apparatus mounted on a track, comprises means to resist the displacement of liquid from a cylinder by a piston when engaged by a vehicle wheel, and a device responsive to vehicle speed to render the means inoperative when the speed is less than a critical value. In Fig. 2, a cylinder 10, 14 has a piston 16 containing a valve housing 25 and a clack valve 26 formed with a cylinder 36. Oil extends to the opening 31 in a piston 28 above which is low-pressure air. On depression of piston 16, a plate valve 37 on cylinder 36, closes holes 35 in valve 26 and liquid flows via holes 34. If vehicle speed is below the critical value, the valve 26 remains open (via holes 34) and disc 33 closes orifice 31, the piston 28 rising against spring 29 and the apparatus produces little or no retardation. For speeds at or above the critical value, the increased liquid flow raises valve 26 against seat 27 to close holes 34, liquid then flowing to chamber 32 via a restricted path including ports 44, 45 in cylinder 36 opened by the rising piston 38 ; the pressure at which the piston rises being determined by spring 39 and the piston cross-section. When the wheel passes over the apex of triangular head 17, piston 16 rises, valve 26 opens, plate 37 drops and liquid flows back to chamber 15. In Fig. 3, the apparatus incorporates an accelerator. Depression of piston 52 into tube 50, 51 forces liquid from chambers 54, 55 to a low-pressure pipe via opening 60 of clack valve 58, ports &c. 61, 62, 63, 64, 65. When vehicle speed is above the critical value, the pressure drop across opening 60 moves valve 58 against seat 66; liquid then flowing via ports 95, 81 in valve sleeve 83 and stem 73, respectively, to move a valve 76 against circlip 78 and then flowing past ball valve 79 to a high-pressure line against the resistance of the high-pressure liquid. When piston 52 approaches its limit position, a ring 90 engages a circlip 94 to move sleeve 83 and register ports 96, 82 permitting flow from stem 75 above valve 76 when piston 52 rises. As piston 52 rises fluid from connection 65 flows into the unit via the opened valve 66. The ring 90 eventually engages circlip 93 to raise sleeve 82 and re-register ports 95, 81, high pressure liquid raising valve 76. When vehicle speed is below the critical value, clack valve 58 remains open and valve 76 remains in its uppermost position due to pressure in stem 75, liquid being displaced to connection 65. Near the end of the stroke of piston 54, circlip 94 displaces sleeve 83 to register ports 96, 82 to supply high-pressure liquid to chamber 54 to force piston 52 upward to impart an acceleration to the wheel, the sleeve 83 being eventually raised as before. A lever 73 prevents the apparatus acting as an accelerator for vehicles moving from left to right in Fig. 3, the lever turning a pivot 72 and through cam 71 depresses a plunger 70 to move seat 66 against clack valve 58, the apparatus then acting as a retarder. The apparatus is rendered inoperative by venting the high-pressure supply to stem 75. In Fig. 6, for speeds above the critical value, piston 101 displaces liquid at a high rate to chamber 106 causing valve 111 to engage seat 116; at a predetermined high-pressure a valve 132 opens and the liquid moves a spool 119 to close an air supply port 134. Pressure liquid flowing via valve ports 113 normally closed by ring 114, to move piston 109 to expel air from chamber 108 until abutment 129 engages and moves flange 128 to close passage 130 and register ports 124, 126. When the piston 109 is fully raised by spring 110 after passage of the vehicle wheel, passage 121, 120 align and liquid escapes from passage 118 to chamber 106; spring 131 returns spool 119 to open port 134. When vehicle speed is below the critical value, liquid passes through valve ports 112 and valve 132 remains closed. Piston 109 moves valve 123 to close passage 130 and register ports 124, 126, compressed-air being supplied to chamber 108 to move piston 109 upwards to force liquid from chamber 106 into chamber 103 causing piston 101 to impart an accelerating force to the wheel. Other embodiments of the accelerating and retarding device are given in the first Provisional Specification and a compressed-air device is described in the third Provisional Specification.